When it comes to HVAC system design, precision isn’t just recommended—it’s essential. That’s why the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has established a series of standards to guide professionals in creating systems that are efficient, safe, and comfortable. Whether you’re a seasoned designer or just starting out, understanding the key ASHRAE standards is foundational to good practice—and often, required by code.
In this post, we’ll break down the most essential ASHRAE standards that every HVAC designer should know and explain how they impact real-world design decisions.
ASHRAE 55 defines the ideal combinations of indoor thermal environmental factors (temperature, humidity, air speed, and radiant heat) that are controllable by the designer, based on personal factors (clothing insulation and metabolic rate) that can be reasonably predicted by the designer.
Comfort is subjective, but this standard provides a quantifiable framework for designing spaces that feel good to most people. It emphasizes the importance of not just reaching a set temperature, but considering the full thermal experience of occupants.
Designers often use ASHRAE 55 to set target conditions for heating and cooling loads. Tools that simulate occupant comfort or adaptive comfort models often rely on this standard for benchmarking.
This standard sets the minimum ventilation rates and other requirements for indoor air quality in commercial and institutional buildings. (For residential buildings, ASHRAE 62.2 is used.)
HVAC systems aren’t just about temperature—they’re also a primary tool for delivering fresh air and removing contaminants. Poor indoor air quality (IAQ) can lead to odours and health issues.
Designers use ASHRAE 62.1 to calculate required outdoor air rates based on occupancy and space type. It also provides guidance on how to properly address exhaust air with various types of contaminants.
ASHRAE 90.1 sets minimum energy efficiency requirements for new buildings and major renovations, including HVAC equipment, insulation, lighting, and controls.
Many building codes across North America use ASHRAE 90.1 as a baseline for energy compliance. Even when not legally required, it serves as a benchmark for good energy-conscious design.
This standard directly influences equipment selection (e.g. SEER or EER ratings), insulation requirements for ductwork and piping, and system control strategies like demand-controlled ventilation.
ASHRAE 189.1 provides guidance for sustainably designed buildings. It incorporates provisions from ASHRAE 55, 62.1, and 90.1, but adds more stringent sustainability targets related to energy use, water efficiency, indoor environmental quality, and construction practices.
With increasing pressure for low-carbon, environmentally responsible buildings, 189.1 is a go-to standard for designers involved in LEED or other green building certifications.
Buildings that meet ASHRAE 189.1 tend to save water, have better energy efficiency, and have happier occupants. Standard 189.1 requirements overlap with other green building programs such as LEED, which encourage more sustainable buildings in all aspects, even including the construction process and building location.
This standard provides ventilation requirements specifically for health care environments such as hospitals, clinics, and labs.
Healthcare settings have higher stakes when it comes to IAQ—airborne pathogens, chemical exposure, and sensitive occupants are major concerns. ASHRAE 170 helps ensure these spaces meet rigorous safety and comfort requirements.
For designers working in healthcare, ASHRAE 170 determines everything from air change rates and pressure relationships (e.g., negative pressure isolation rooms) to filtration standards.
While knowing the standards is one thing, applying them effectively requires the right approach:
Use software that aligns with ASHRAE standards. Many load calculation and energy modeling tools (like EnergyPlus, Carrier HAP, or HeatWise) are built with ASHRAE compliance in mind.
Stay up-to-date. ASHRAE standards are revised regularly. Subscribe to ASHRAE updates or join a local chapter to stay informed.
Cross-reference your building codes. Many jurisdictions integrate ASHRAE standards into their codes, but with modifications. Always check your local authority having jurisdiction (AHJ).
Understanding ASHRAE standards isn’t just about passing inspections—it’s about designing HVAC systems that are comfortable, efficient, and built to last. Whether you’re optimizing thermal comfort with ASHRAE 55, ensuring healthy indoor air with 62.1, or meeting energy targets with 90.1, these standards serve as your roadmap to responsible and effective design.
By integrating them into your design process, you elevate not only the performance of your systems, but also the quality of the environments they support.
